fix: do not create 1:1 chat on second device when scanning a QR code

This avoids creating 1:1 chat on a second device when joining a channel.
Now when joining a channel there may be no 1:1 chat with the inviter
when the channel is created. In this case we still create the channel
as unblocked even if 1:1 chat would be a contact request
because joining the channel is an explicit action
and it is not possible to add someone who did not scan a QR
to the channel manually.

python/tests/test_0_complex_or_slow.py

@@ -288,6 +288,7 @@ def test_use_new_verified_group_after_going_online(acfactory, data, tmp_path, lp
     assert open(contact.get_profile_image(), "rb").read() == open(avatar_path, "rb").read()
 
     lp.sec("ac2_offl: sending message")
+    chat2.accept()
     msg_out = chat2.send_text("hello")
 
     lp.sec("ac1: receiving message")